Generally, ring resonators have been known and used to select an electromagnetic wavelength. In addition, ring resonators can be used to sense chemical substances and bio-agents. The advantage of using ring resonators is that when provided with energy of electromagnetic wave or light, a resonance condition can be established and can be determined.
U.S. Pat. No. 5,663,790, to Eckstrom, et al., utilizes the resonance condition of the ring resonator for determining the refractive index of the ring resonator, which can be used to determine the quality and quantity of a sample. Eckstrom appears to disclose an apparatus and method for sensing sampled materials that includes a first ring resonator for sensing sampled materials and a second ring resonator for sensing referenced materials. The apparatus further includes a straight waveguide for inputting light. The straight waveguide also senses a change in wavelengths of the light from first and second resonators that are exposed to the sampled materials and referenced materials, respectively. The change in wavelength of the light caused by the referenced materials and the sampled materials can be processed to determine the refractive index of the ring resonator.
The index of refraction is a specific expression of a dielectric constant in optical wavelength range. Thus, the measurement of index refraction utilizes only a small spectrum of electromagnetic wave in order to measure the change in optical wavelength.
From the above, it can be appreciated that it would be desirable to have an apparatus and method for utilizing the entire spectrum of electromagnetic wave to detect sample materials. It can also be appreciated that it would be desirable to have an apparatus and method that can determine the change of effective dielectric constant by detecting the change in the power of the electromagnetic wave in the circular resonator due to the coupling of the sample materials to the circular resonator. It can also be appreciated to have an apparatus and method that can detect the change in the power of the electromagnetic wave in the circular resonator at resonance condition and/or during a build-up stage.